Transfer film for use with a flexible circuit compression connector

ABSTRACT

A flexible circuit compression connector system utilized to electrically connect together conductive pads disposed on a rigid printed circuit board, the connector system comprising a flexible insulating substrate having conductive material at a plurality of preselected positions and a conductive line extending between at least two of the preselected positions, a plurality of contacts, each contract secured to the flexible substrate at each of the preselected positions having conductive material, a compression assembly that includes a resilient compression mat and means for aligning the flexible substrate of the compression assembly and the rigid substrate together so that the resilient compression mat urges the contacts secured to the flexible substrate against the conductive pads on the printed circuit board. A method of manufacturing the flexible circuit compression connector system that includes a compression assembly by forming the contacts into a preselected configuration and securing the contacts to the flexible substrate is also included.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation-in-part of pending U.S.patent application Ser. No. 08/963,401 filed Nov. 3, 1997 entitled“COMPRESSION CONNECTOR”.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to electrical connectors and, moreparticularly, to high density electrical connectors utilized toelectrically connect electronic devices disposed on two or more printedcircuit boards.

[0004] 2. Description of the Prior Art

[0005] Increased integration of electronic devices has created aninterconnection problem for printed circuit boards receiving thesedevices. Specifically, the number of interconnections required toelectrically connect together two or more printed circuit boardsreceiving these electronic devices has exceeded the connection densitiesof prior art pin-in-socket connectors. Moreover, these prior artpin-in-socket connectors typically have relatively long and unshieldedlengths which have uncontrolled impedances resulting in less thandesired electrical performance.

[0006] A high contact density connector utilizable for electricallyconnecting together electronic devices received on two or more printedcircuit boards and overcoming the foregoing problems is disclosed in anarticle entitled “A High Density Edge Connector” by J. Campbell et al.,Copyright 1995 IEEE. This article discloses a flex circuit formed of a 2mil thick polyamide film having 3 mil wide copper lines plated onto oneside thereof and 25 mil round contact pads plated on the side of thefilm opposite the circuit lines and along both edges of the film. 4 mildiameter plated through-holes, or vias, extend between the contact padson one side of the film and the circuit lines on the other side.Palladium dendrites, or spires, are electro-deposited on surfaces ofeach contact pad. These dendrites straddle dust or fibers and punctureoils or films present on each contact pad prior to connector mating andproduce on each contact pad a multitude of conductive connections. Theconnector includes a molded plastic force block to which elastomericcylinders are molded. These cylinders act as springs which provideforce, when compressed during assembly, to make and maintain anelectrical connection between the contact pads on the film and the padson a printed circuit board. One cylinder is provided for each contactand compensates for any variation in planarity and toleranceaccumulation. Conical alignment pins are utilized to mate alignmentholes in the flex circuit with alignment holes in the printed circuitboard during assembly, thereby ensuring proper registration between thecontact pads on the film and the pads on the printed circuit board.

[0007] Another flexible circuit connector for connecting a daughter cardand a mother board is disclosed in an article entitled “A High DensityPad-On-Pad Connector Utilizing A Flexible Circuit” by R. S. Pokrzywa,Copyright 1993 IEEE. This connector utilizes a two-sided flex circuithaving plated, spherical contacts contacting flat printed circuit padson the daughter card and on the mother board. The spherical contacts onthe flex circuit are 5 mils in diameter and have a copper base metaloverplated with nickel and gold. Alignment pins are utilized to alignthe flex circuit, the daughter card and the mother board so that eachspherical contact mates with a desired printed circuit pad.Precipitation hardened stainless steel curved beams provide contactforce for reliable connection between the spherical contacts and theprinted circuit pads. During actuation, the curved beam is flattened toproduce a uniform load across the contact area. An elastomeric pad ispositioned between the beam and the contact area to accommodate localdiscrepancies in load across the contact area and to focus the connectorforces. In one embodiment, the elastomeric pad has a plurality ofelastomeric cylinders utilized to back-up the spherical contacts. Inanother embodiment, where size does not permit molding individualcylinders for each spherical contact, an elastomeric rib is utilized toback a row of spherical contacts.

[0008] A problem with spherical contact pads and electro-depositeddendrites on contact pads is that they inconsistently break throughcontaminants, such as oxides, films or foreign materials, that may bepresent thereon or on the contact pad of a printed circuit board. Hence,inadequate electrical contact or, in some instances, no electricalcontact is made between the contact pad of the flexible circuit and thecontact pad of the printed circuit board. Moreover, the formation of ageometric surface such as dendrites or spheres on the contacts of theflexible circuit increases the cost of such connectors.

[0009] Currently available flexible circuits are expensive tomanufacture and must be designed for specific applications. What isdesired is a flexible electrical connector device that includes acompression means, yet is adaptable to different applications and isinexpensive to manufacture.

[0010] It is therefore an object the present invention to provide aflexible circuit compressor connector system that includes a compressionassembly device which overcomes these drawbacks of the prior artconnectors. It is a further object of the present invention to provide aflexible circuit compression connector system contact that promoteselectrical contact with conductive pads of a printed circuit boardtailored to specific applications. It is an object of the presentinvention to provide a method for making a flexible circuit compressionconnector system that utilizes a resilient compression assembly deviceto provide the required contact. It is an object of the presentinvention to provide a method of making a flexible circuit compressionconnector system that includes a resilient compression assembly that isless costly to manufacture than the prior art flex circuit connectorsand is easy to assemble and align.

SUMMARY OF THE INVENTION

[0011] Accordingly, we have invented a flexible circuit compressionconnector system that includes a compression assembly utilized toelectrically connect together conductive pads disposed on one or moresubstrates. The flexible circuit compression connector system includes aflexible insulating substrate having a plurality of predeterminedpositions of preapplied conductive material and at least one conductiveline thereon extending between at least two of the predeterminedpositions of preapplied conductive material, such as a solder paste. Thesystem also includes a plurality of contacts of preselectedconfiguration forming a matrix which are assembled to the substrate.Each contact has a head and a base secured to the flexible insulatingsubstrate at the predetermined positions of conductive material, therebyforming a contact matrix. The base and head are conductive materials.Each contact in the matrix has a head of preselected configurationextending away from the base and the flexible substrate. Each contact isconductive so as to allow a flow of current through the preappliedconductive material on the substrate and the base through thepreselected configuration of the contact. In one configuration, theflexible circuit compression connector system includes a flexiblesubstrate having a plurality of conductive holes therein and at leastone conductive line thereon extending between at least two of theconductive holes. The flexible circuit compression connector system alsoincludes a plurality of contacts. Each contact includes a base and ahead that extends away from the base. Optionally the base may include apost that extends away from the base in a direction opposite the head.The base or the optional post of each contact is secured in one of theplurality of conductive holes.

[0012] A compression mat is positioned on the side of the flexiblesubstrate opposite the heads of the plurality of contacts. Thecompression mat includes a plurality of resilient cylinders extendingaway from a resilient base. Each resilient cylinder has a distal endalignable with each one of the plurality of contacts, but on the side ofthe flexible substrate opposite the contact heads.

[0013] In assembling the contacts to the flexible substrate, a transferfilm is utilized to transfer the plurality of contacts to the flexiblesubstrate. The disposable transfer film preferably has a plurality ofelastically deformable receiving apertures which receive and secure thehead portion of preselected configuration of the plurality of contacts.

[0014] A flexible cable assembly is attached to a first substrate, suchas a rigid printed circuit board, which has a plurality of theconductive pads on a surface thereof and at least one conductive lineconnected to at least one of the conductive pads. The rigid substrateand the flexible circuit compression connector system are alignable sothat a portion of the head of each contact on one end of the flexiblesubstrate is aligned in registration with one of the conductive pads onthe surface of the rigid substrate.

[0015] A means for compressing the compression mat against the contactsis positionable adjacent the resilient base of the compression mat. Themeans for compressing urges together at least a portion of the head ofeach contact on one end of the flexible cable to the conductive pad ofthe printed circuit board or assembly in registration therewith. Theresilient columns of the compression mat contact the side of theflexible substrate opposite the heads of the contact matrix of theflexible substrate so that each resilient column is aligned opposite acontact of the contact matrix. The resilient columns act as springs whencompressed and urge the contact heads on the contact matrix of theflexible substrate against the conductive pads on the surface of themating assembly, typically the rigid substrate such as a printed circuitboard. In an alternative configuration, each resilient column of thecompression mat contacts the distal end of an optional post of acontact, the post extending through the flexible substrate and functionsas the spring when compressed to make and maintain good electricalconnection between the contact head and corresponding conductive pad.

[0016] Preferably, a plurality of alignment holes in each of theflexible substrate, the rigid substrate and a surface that includes thecompression mat co-act with plurality of alignment members to align theflexible substrate, the rigid substrate and the compression mat so thatthe resilient cylinders are in registration with the contacts, and theheads of the plurality of contacts are in registration with theplurality of conductive pads. Each alignment member may be threaded andmay serve the dual purpose of producing the compressive force forcompressing the mat against the flexible substrate opposite the heads.

[0017] The present invention is a flexible circuit compression connectorsystem comprised of at least one contact that includes a conductive headand a conductive base. The conductive head extends from one side of thebase and is of a preselected design most suitable for its intendedapplication. An optional post may extend from the side of the baseopposite the head.

[0018] The base of the contact is secured to the flexible substrate atpredetermined positions with a conductive material such as solder whilea preformed head of preselected configuration extends away from thebase. In an alternative configuration, the side of the base opposite thepost can have a cavity formed therein in registration with a lengthwiseaxis of the post. The base can have a periphery having a generallyrectangular outline. Each corner of the generally rectangular outline ofthe base can be rounded and can include one of the plurality ofprojections. Each projection can have a rounded edge formed continuouswith the periphery of the base.

[0019] The present invention includes a method of making a flexiblecircuit compression connector system that includes a compressionassembly having a connector that includes providing a plurality ofcontacts forming a matrix, each contact having at least a base and ahead of preselected configuration selected on the basis of its intendedapplication, the head projecting away from the base. The contacts arepreformed by a metal working operation into any suitable preselectedhead geometry, the contacts being connected together by ribs. The headsof the plurality of contacts are inserted into a plurality of receivingapertures in a thin transfer film which captures the contacts so thatthe heads project through one side of the transfer film while a portionof the contacts are projected from the opposite side of the film. Thinribs connecting the contacts are then separated from the contacts. Aflexible insulating substrate is provided with preapplied conductivematerial applied at a plurality of predetermined positions. At least oneconductive line extends between and electrically connects at least twoof the predetermined positions of preapplied conductive material. Thetransfer film containing the contacts and the flexible substrate aremated by bringing the side of the transfer film having the portion ofthe contacts projecting from the transfer film opposite the heads intoregistry with the preapplied conductive material on the flexiblesubstrate. This portion may be bases or optional posts. By applicationof heat, the contacts are fused to the preapplied conductive material onthe flexible substrate. The transfer film is then separated from theflexible substrate so that the heads of the contacts project away fromthe surface of one side of the flexible substrate.

[0020] In the alternative configuration, a method of making the flexiblecircuit compression connector system that included a connector thatincludes providing a plurality of contacts, each contact having a basewith a post and a head. The heads of the plurality of contacts areinserted into a plurality of receiving apertures in a disposabletransfer film so that a portion of the post connected to the baseopposite the head extends out of the plurality of receiving apertures. Aflexible substrate is provided having a plurality of through-holestherein and a plurality of conductive lines thereon. At least oneconductive line extends between and electrically connects at least twoof the through-holes into which the conductive bases are inserted. Thethrough-holes preferably are conductive. The transfer film and theflexible substrate are mated so that at least a portion of each base ofthe plurality of contacts are received in the plurality of conductivethrough-holes in the flexible substrate. The portion of the bases, whichmay be the aforementioned posts, of the plurality of contacts are fusedto the plurality of through-holes in the flexible substrate. Thetransfer film is then separated from the flexible substrate and theplurality of contacts.

[0021] The plurality of contacts are formed from a strip of conductivematerial by any conventional metal forming method. Each contact isconnected to an adjacent contact by a rib formed from the conductivematerial strip during the metal forming operation. Each contact isexcised from its connecting rib after insertion into one of thereceiving apertures in the transfer film. Each receiving apertureelastically deforms to receive and retain the contact therein.

[0022] An advantage of the present invention is that it provides aflexible cable including a compression assembly which overcomes thedrawbacks of the prior art connectors. The present invention provides aflexible circuit compression connector system having a compressionassembly that includes an electrical connector that utilizes thecompression assembly to promote positive contact between the connectorand the conductive pads of a mating circuit. The present invention alsoprovides an improved method for making a flexible circuit compressionconnector system that utilizes the provided compression assembly toassure positive contact with a mating assembly. The present inventionalso provides a method of making a flexible electrical cable andconnector that is easier, more reliable, more readily adaptable tomodifications, including field modifications, and less costly tomanufacture than the prior art flex circuit connectors.

[0023] Other features and advantages of the present invention will beapparent from the following more detailed description of the preferredembodiment, taken in conjunction with the accompanying drawings whichillustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1a is a cross section of one embodiment of a flexible circuitcompression connector system in accordance with the present invention;

[0025]FIG. 1b is an enlarged view of a portion of FIG. 1a withinrectangle 1 b;

[0026]FIG. 2a is a plan view of a compression mat of the compressionassembly in FIG. 1;

[0027]FIG. 2b is a side view of the compression mat of FIG. 2a;

[0028]FIG. 3a is a cross-section of a second embodiment of a flexiblecircuit compression connector system in accordance with the presentinvention;

[0029]FIG. 3b is a an enlarged view of a portion of FIG. 3a withinrectangle 3 b;

[0030]FIG. 3c is a cross-section of flexible substrate prior toattachment of contacts;

[0031]FIG. 4 is an exploded view of an embodiment of flexible substratewith an optional contact configuration;

[0032]FIG. 5a is a cross-section of the preferred embodiment of theflexible circuit compression connector system of the present inventionconnected to a rigid circuit board;

[0033]FIG. 5b is an enlarged view of the flexible circuit compressionconnector system connected to a rigid circuit board of FIG. 5a;

[0034]FIG. 5c is a plan view of a connector block of the compressionassembly that forms part of the flexible circuit compression connectorsystem of FIG. 5b;

[0035]FIG. 5d is a cross-section of the connector block of FIG. 5c;

[0036]FIG. 5e is a cross-section of the compression assembly of FIG. 5d;

[0037]FIG. 6a is a plan view of one embodiment of a flexible substrateused in the compression connector of FIG. 1;

[0038]FIG. 6b is an enlarged view of a portion of FIG. 3a within line 3b;

[0039]FIG. 7a is a plan view of a conductive strip that has been formedto include a plurality of contacts that are utilized in the compressionconnector of FIG. 1;

[0040]FIG. 7b is an enlarged view of a portion of the conductive stripof FIG. 7a within rectangle 7 b;

[0041]FIG. 7c is a cross section taken along lines 7 c-7 c in FIG. 7b;

[0042]FIG. 8 is a plan view of the conductive strip of FIG. 7a alignedwith a transfer film;

[0043]FIG. 9a is a cross-section of one configuration of an alignedconductive strip and transfer film of FIG. 8 positioned between atransfer base and an excising tool;

[0044]FIG. 9b is a cross-section of an alternative configuration of aconductive strip and transfer film of FIG. 8 positioned between atransfer base and an excising tool;

[0045]FIG. 10 is a cross section of the contacts of the conductive stripof FIG. 7a received in receiving apertures of the transfer film of FIG.9a after excising ribs and positioned in alignment with through-holesformed in the flexible substrate of FIG. 3a;

[0046]FIG. 11 is a cross section similar to FIG. 10 showing the transferfilm and flexible substrate mated together with the posts of thecontacts received within and soldered to the through-holes of theflexible substrate; and

[0047]FIG. 12 is a cross section similar to FIGS. 10 and 11 and showingthe separation of the transfer film from the flexible substrate andcontacts.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0048] Referring to FIGS. 1a-1 b, a rigid substrate 2, such as a rigidprinted circuit board formed of FR-4 or ceramic, has a plurality ofconductive pads 4 formed thereon in a manner known in the art. The rigidsubstrate 2 may include one or more conductive lines that extend betweenone or more of the conductive pads 4 or between a conductive pad 4 andan electronic device connected to the rigid substrate 2. The conductivelines and electronic device are not shown on the rigid substrate 2 inFIG. 1 for simplicity of illustration.

[0049] A flexible circuit compression connector system 5 comprised of aflexible insulating substrate 6 having a plurality of contacts 8 securedthereon is positioned adjacent the rigid substrate 2. The flexiblesubstrate 6 is preferably formed of a polyimide film such as Kapton® orMylar. Kapton® is a registered trademark of E. I. DuPont DeNemours &Company. The contacts 8 are secured to the flexible substrate 6 in apattern matching the pattern of the conductive pads 4 on the rigidsubstrate 2. Each contact 8 includes a head 10 that extends away from asurface of the flexible substrate 6. Aligning the flexible substrate 6and the rigid substrate 2 positions the heads 10 of the flexiblesubstrate 6 in registration with the conductive pads 4 of rigidsubstrate 2.

[0050] In accordance with one embodiment of the present invention shownin FIG. 1a, a compression assembly 12 is positioned on the side of theflexible substrate 6 opposite the heads 10 of the contacts 8 to form theflexible circuit compression connector system 5. The compressionassembly 12 includes a compression mat 14 received in an aperture 15 ofan alignment sleeve 16. As shown in FIGS. 2a-2 b, the compression mat 14includes a base 18, preferably having a generally rectangular outline,and a plurality of resilient cylinders 20 extending from the base 18.The compression mat 14 and the flexible substrate 6 are positioned sothat distal ends of the resilient cylinders 20 are aligned inregistration with the contacts 8 on a surface of the flexible substrate6 opposite the heads 10. The compression assembly 12 further includes awasher 22 positioned on a side of the alignment sleeve 16 adjacent thebase 18 of the compression mat 14. Although the alignment sleeve andwasher may be a single element, preferably, the compression mat 14, thealignment sleeve 16 is formed from a polyphenylene sulfide, UL 94 V-O,the washer 22 is formed from stainless steel and the compression mat 14is formed of a thermal silicon rubber.

[0051] The compression assembly 12, flexible substrate 6 and the rigidsubstrate 2 each have a plurality of alignment apertures 24, 26 and 28,respectively. In the arrangement shown in FIG. 1a, the apertures extendthrough the compression assembly, the flexible substrate and the rigidsubstrate. Each alignment aperture 24, 26 and 28 is adapted to receive ashaft of an alignment member 30, such as a bolt having an externallythreaded end 31 adapted to mate with internal threads of a nut 32.Applying the nuts 32 to the threaded portion of alignment members 30urges together the compression assembly 12, the flexible substrate 6 andthe rigid substrate 2. This urging together forces into contact theconductive pads 4 and the heads 10 in registration therewith, and thedistal ends of the resilient cylinders 20 in registration with contacts8 on the surface of the flexible substrate 6 opposite the heads 10.Continued tightening of nuts 32 to the threaded ends of alignmentmembers 30 compresses the compression mat 14 between the flexiblesubstrate 6 and the washer 22. This compression causes the resilientcylinders 20 to deform elastically against the contacts 8 on the side offlexible substrate 6 opposite heads 10. This deformation causes eachresilient cylinder 20 to apply a spring force to the head 10 and thus tothe conductive pad 4 in registration therewith. This spring forcebetween the head 10 and the conductive pad 4 in registration therewithprovides the basis for formation and maintenance of good electricalcontact, while compensating for any variations in planarity andtolerance accumulation. In the embodiment shown in FIG. 1a, preferably,double-sided tape 34 is utilized to adhere together adjacent surface offlexible substrate 6 and the sides of the alignment sleeve 16. Flexiblesubstrate 6, however, may be attached to compression assembly 12 by anymeans suitable to form flexible circuit compression connector system 5.

[0052] In the configuration shown in FIGS. 1a and 1 b, head 10 of eachcontact 8 has a base 40 and a plurality of projections 42 disposedaround a periphery 43 of the base 40. The projections 42 extend to oneside of the base 40 and give the head 10 a crown-shaped appearance. Eachcontact 8 also has a post 44 that extends from a central part of thebase 40 opposite the projections 42. A cavity 46 is formed in each base40 opposite the post 44 and in alignment with a lengthwise axis 47 ofthe post 44.

[0053] Although projections 42 in the configuration shown in FIGS. 1aand 1 b provide head 10 with a crown shaped appearance, each contact 8has a base 40 and a head 10 of preselected configuration. Theconfiguration of the head 10 is not limited to the crown shapedconfiguration depicted in FIGS. 1a and 1 b. Heads 10 may be of anypreselected configuration, and as will be become apparent, may vary fromposition to position on any flexible circuit compression connectorsystem, if so desired. Regardless of head configuration, as should beclear to one skilled in the art, contact 8 may assume any form orcombination of forms in which the contact has at least a base 40 and ahead 10 extending away from base 40. Preferably, head 10 of each contact8 extends away from the base 40 when assembled to flexible substrate onthe side of the base 40 opposite flexible substrate 6. Each contact 8 issecured to flexible substrate 6 in a positive manner to assure areliable current flow.

[0054] In a second embodiment of the flexible circuit compressionconnector system as shown in FIGS. 3a, 3 b, and 3 c, flexible substrate806 is a planar body of substantially uniform thickness, as shown. Itwill be understood that the thickness of substrate 806 may be varied asneeded. A conductive metallic material 850, such as solder, ispreapplied to the flexible substrate 806 at preselected positionscorresponding to required conductive pads 4 on rigid substrate 2.Conductive metallic material 850 is preferably connected to at least oneconductive line 852 or to one or more conductive ground planes (notshown) formed on the flexible substrate surface that extends between atleast 2 of the preselected positions as shown in FIG. 3c. In thisembodiment, the one or more conductive ground planes are formed on thesame surface of the flexible substrate as the conductive line. Suchconductive ground planes reduce or eliminate cross-talk betweenconductive lines and/or reduce or eliminate the effect on one or more ofconductive lines 852 of electro-magnetic interference from externalsources. Furthermore, because conductive lines 852 and conductive groundplanes are formed on one side of the flexible substrate 806, thepossibility of metallic material extending through any apertures in thesubstrate to act as an electrical antenna and becoming a source ofinterference is eliminated. In this embodiment as shown in FIG. 3c priorto application of contacts 808, the circuitry on the flexible substrateis more dense and the application of conductive metallic material 850such as solder must be better controlled than in the previousembodiment. It will be understood that while solder is the most costeffective material for this application, other conductive materials suchas copper or its alloys may be applied by suitable techniques, such asplasma depositing, spraying, laser depositing, plating or any othersuitable method. Flexible circuit compression connector system comprisedof compression assembly 12 which is otherwise identical to compressionassembly 12 depicted in FIGS. 1a and 1 b, is assembled to flexiblesubstrate 806 to form flexible circuit compression connector system 805.

[0055] In a variation of this embodiment of the invention as shown inFIG. 4, flexible substrate 906 includes cavities 948 or depressions atpredetermined locations on its surface corresponding to contact padpositions 4 found on rigid substrate 2. Cavities 948 or depressions havea depth less than the thickness of flexible substrate 906. Conductivelines 952 or conductive ground planes (not shown) extend between atleast two of the cavities 948 on the flexible substrate. In thisembodiment, each contact 908 has a post 944, a base 940 and a head 910of preselected configuration. Head 910 of each contact 908 extends awayfrom the base 940 on the side of the base opposite the flexiblesubstrate 906. Post 944 of each contact 908 is dimensioned to be aboutthe same as the dimensions of the corresponding cavity 948 in theflexible substrate 906. It will be understood by those skilled in theart that the height of post 944 will closely correspond to the depth ofcavity 948, while the lateral dimensions of each post 944 may beslightly larger than, identical to or slightly smaller than thedimensions of each cavity 948. The choice of the lateral dimensions willdepend on the chosen method of securing contact 908 to substrate 906.For example, if an interference fit between the post 944 and thecorresponding cavity 948 is desired, the post lateral dimension isslightly larger than the cavity dimension, and solder 942 is preappliedto the cavity. If liquid solder is to be flowed over the flexiblesubstrate and into cavity 948, then the post dimension is slightlysmaller than the cavity dimension so that the liquid solder can beintroduced into the cavity, for example, by capillary action. It will beunderstood that a compression assembly such as is shown in FIGS. 1a, 1b, 3 a, or 3 b or as will be described, is utilized in conjunction withflexible substrate 906 to form a flexible circuit compression connectorsystem (not shown) to urge head 910 on the flexible substrate 906 intocontact with conductive pads 4 of substrate 2.

[0056]FIG. 5a depicts a preferred embodiment of the flexible circuitcompression connector system of the present invention assembled to arigid substrate 2 such as the circuit board as previously described.Rigid substrate 2 includes conductive pads 4, conductive lines (notshown) extending between on of more of conductive pads 4. A flexiblecircuit compression connector system 512 is comprised of a flexibleinsulating substrate 506, a connector block 550, and a resilientcompression mat 14 having resilient compression cylinders 20. FIG. 5b anenlarged view of a portion of FIG. 5a. Resilient mat 14 is assembledonto connector block 550. A plan view of the preferred embodiment ofconnector block 550 is shown in FIG. 5c, and in cross section in FIG.5d. Connector block 550 is made of an insulating material. The connectorblock itself may be made of a compressible nonconducting material, butin the embodiment shown, block 550 is made of a rigid material. Whilethe connector block may be made from any low shrinkage thermoset orthermoplastic material that is readily moldable or workable into a shapehaving the desired features, the blocks are currently manufactured ofpolyphenylene-sulfide. Block 550 as shown is rectangular, but may be anyacceptable shape. At least one aperture 552 extends through block 550.As shown in FIG. 5d, block 550 has a top surface 554, a bottom surface556 and two end surfaces 558 and includes a pair of apertures 552. Twoside surfaces 555 similar to top surface 554 run parallel to the planeof FIG. 5d and extend perpendicularly inward into the plane of FIG. 5c.Top surface 554 includes two extensions or lips 560 extending upwardfrom top surface 554 that are coaxial with apertures 552. Between theselips 560 along top surface is a recess 562. Block 550 as depicted inFIG. 5c also includes optional chamfer 559 thereby eliminating a sharpcorner that could serve as a stress riser for a flexible circuit. Achamfer or a radius (not shown) can be utilized on each edge toeliminate potential stress risers, if desired. Apertures 552 includecounterbores 564 positioned along bottom surface 556. It will beunderstood that this counterbore may be positioned along top surface 554or that a counterbore may be positioned at both ends of each aperture,these structures all being equivalent. Furthermore, a recess identicalto recess 562 optionally may be included on each of side surfaces 555and additionally on bottom surface 556. Lips 560 and apertures 552optionally may be included on any surface that has recesses toaccommodate additional connection. The lips and apertures assist inaligning the assemblies, while the geometry of the adjacent surfaceslimit applied forces as will become apparent.

[0057] Referring now to FIG. 5e, a resilient compression mat 14, such asis shown in FIGS. 2a and 2 b is assembled into recess 562 along topsurface 554 of block 550. Mat 14 includes resilient cylinders 20extending away from mat base 18. Recess 562 is dimensioned andtoleranced to not only accept mat 14, but also to center mat 14 in theproper position along surface 554. Although not shown in thisembodiment, it will be understood by those skilled in the art thatoptional recesses identical to recess 562 in each of side surfaces 555parallel to the plane of FIG. 5e as noted above and bottom surface 556may also accept a mat similar to mat 14. Mat 14 preferably isprefabricated with an adhesive 525 applied to mat base 18 on the sideopposite resilient cylinders 20, so that a protective paper can bepeeled from the adhesive and the prefabricated mat 14 can be assembledinto recess of 562 of block 550 as required. Alternatively, adhesive maybe applied to block 550 as needed and mat 14 may be applied to theadhesive. Threaded insert 570 is assembled into counterbore 564.Although shown in FIGS. 5a, 5 b and 5 e as an insert added tocounterbore 564 in the preferred embodiment, the threaded insert may bemolded into block 550 when block 550 is fabricated so as to be anintegral part of block 550. In the preferred embodiment shown in FIGS.5a, 5 b, 5 c, 5 d, and 5 e, recess 562 is present to accept mat 514 andpresents a convenient means for positioning mat 514 along surface 554 oralong the side surfaces 555. However, these recesses are not necessaryas long as mat 514 can be accurately located along surface 554 so thatresilient cylinders 20 are in a position against the portion of flexiblesubstrate 506 opposite contacts 508 to urge contacts 508 againstconductive pads 4 on rigid substrate 2 as shown in FIGS. 5a and 5 b.Once compression assembly 512 which includes threaded insert 570 orequivalent is assembled by affixing resilient compression mat 514 ontoconnector block 550, flexible circuit compression connector system isassembled by attaching flexible substrate 506 to compression assembly512. Flexible substrate 506 may be permanently affixed to compressionassembly 512 by application of adhesive, if desired. As shown in FIGS.5a and 5 b, alignment apertures 526 in flexible substrate slides overlips 560 to properly align contacts 508 on flexible substrate 506 withcompression cylinders 20 of flexible mat 14, compression cylinders 20extending above surface 554 but below the top of lips 560, formingflexible circuit compression connector system 555. Rigid substrate 2includes alignment apertures 28, the outer diameter of lips 560 beingsmaller than the diameter of alignment apertures 28. Flexible circuitcompression connector system 555 is readily assembled to rigid substrate2 by inserting lips 560 into alignment apertures 28. Threaded fasteners580 having bearing surface 582 are assembled through alignment apertures28 of rigid substrate 2 and apertures 552 to threadably engage threadedinsert 570, so that the engagement urges bearing surface 582 intocontact with rigid substrate 2, which in turn urges resilient cylinders20 in compression assembly 512 against contacts 8 so that heads 10 offlexible circuit compression connector system 505 positively engageconductive pads 4 in the manner previously described. This geometry, inwhich the resilient cylinders 20 extend above surface 554 but below thetop of lips 560, is selected to urge the contacts of the flexiblesubstrate against the conductive pads. However, when appropriatelydimensioned, it provides the additional advantage of self-limiting theresulting faces from the cylinders against the contacts on the flexiblesubstrate, so that over tightening the circuit compression connectorsystem against the rigid circuit board and thereby deforming thecylinders out of alignment with the contacts cannot occur.

[0058] Flexible substrates 6, 506, 806 and 906 include severalembodiments that can be assembled to the compression assemblies of thepresent invention to produce a variety of flexible circuit compressionconnector systems suitable for various applications. In addition, morethan one flexible substrate can be assembled to compression assembly 506to provide a flexible circuit compression connector system with multipleconnectivity capabilities.

[0059] With reference to FIGS. 6a-6 b and with ongoing reference toFIGS. 1a-1 b, flexible substrate 6 has a plurality of through-holes 48formed therein that are adapted to receive the posts 44 of the contacts8. The wall of each through-hole 48 includes metallization 50 formedtherein to form a conductive through-hole. The metallization 50 in eachthrough-hole 48 is preferably connected to a conductive line 52 or toone or more conductive ground planes 53 formed on the flexible substrate6. The one or more conductive ground planes 53 are formed on one or bothsurfaces of the flexible substrate 6 to reduce or eliminate cross-talkbetween conductive lines 52 and/or to reduce or eliminate the effect onone or more of the conductive lines 52 of electro-magnetic interferencefrom external sources. The metallization 50 in each through-hole 48, theconductive lines 52 and the conductive ground planes 53 are formed onthe flexible substrate 6 in a manner known in the art. To maintain post44 of each contact 8 received in a through-hole 48, the metallization 50of each through-hole 48 and the posts 44 of the contacts 8 receivedtherein are fused together, preferably utilizing a solder 54.

[0060] In different embodiments, as shown in FIGS. 3b and 4, flexiblesubstrate 806, 906 does not contain through holes 48 that extend throughthe flexible substrate. Rather, contacts 808, 908 are positioned on onlyone side of substrate 806, 906. Conductive ground planes and conductivelines 852, 952 are positioned on the same side of the substrate.Contacts 808, 908 are assembled to the flexible substrate in a similarmanner; however in one embodiment, no posts are utilized. Referring nowto FIGS. 3a and 3 b, a flexible circuit having a pattern similar to thecircuit shown in FIGS. 6a and 6 b but without through holes, hascontacts assembled to conductive metallic material 850 such as solderthat is deposited at plurality of preselected locations corresponding topositions of metallization 50 such as is shown in FIG. 6a. Ground planesand conductive lines extend between at least two of such preselectedlocations. Contacts 808 include a base 840 and a head 810, but no post.Contacts are adhered to substrate 806 by bringing base 840 of contactsinto alignment with conductive metallic material 850 and applying heatto adhere base 840 to metallic material. This can also be accomplishedby reflow soldering, or alternatively by wave soldering, a well-knowntechnique in which a wave of liquid solder is flowed over the substrateor if 850 is preapplied solder, by simply heating to liquify the solder.

[0061] In a variation of this embodiment as shown in FIG. 4, flexiblesubstrate 906 includes recesses, depressions or cavities 948 which donot extend completely through substrate 906. Cavities 948 are located ata plurality of preselected locations corresponding to positions 50 suchas is shown in FIG. 6a. Contacts 908 include a head 910, a base 940 anda post 944. The post is designed for assembly into cavity 948 andcontacts are assembled to flexible substrate 906 by introducing aconductive metal such as solder 94 into cavity 948, thereby bondingcontacts to flexible substrate 906 as previously described.

[0062] In still another variation which is a hybrid of theabove-described embodiments, flexible substrate (not shown) includes acombination of through holes that extend through flexible substrate,such as through holes 48, and preselected positions for contacts andthat are positioned on only one side of flexible substrate, thepreselected positions for contacts and through holes forming an array inwhich the preselected positions for contacts and through holes occupyalternating positions on the array. With this configuration, conductivelines can be positioned on one side of the flexible substrate and canrun between the contacts and conductive ground plans can be positionedon the opposite side of the substrate and can run between the throughholes. Conductive lines extend between at least two of the contacts onone side of the opposite side of the flexible substrate. As will becomeapparent, the present invention allows for assembly of an array ofcontacts into positions on the array of through holes and preselectedpositions for contacts such that contacts at alternating positions willinclude a base, a head and a post that are secured to metallized throughholes while adjacent contacts will include a base, a head and optionallya post that are secured to the preselected positions adjacent thethrough holes. In this configuration, although the density of the arrayof contacts remains the same, the circuitry is less dense since theconductive ground planes are positioned on one side of the flexiblesubstrate, being connected by the contacts secured to the flexiblethrough holes, while the conductive lines and its associated circuitryare located on the opposite side of the flexible substrate. Furthermore,there should be no problems with apertures in the substrate acting aselectrical antenna and becoming sources of interference, as previouslydescribed, when the apertures only receive contacts connected to groundplanes.

[0063] The array of contacts that can be assembled to flexible substrate6, 506, 806 and 906 include several different embodiments andcombinations of these embodiments. Although the configuration ofcontacts may vary depending upon the particular characteristics of thecircuit in which the flexible circuit compression connector system is tobe used, the method of forming the contacts and assembling the contactsto flexible substrate is essentially the same. With reference to FIGS.7a-7 c, an array of contacts 8 having a preselected configuration isformed in a preferred embodiment by exposing a thin, flat strip 60 ofconductive material to a stamping operation. The stamping operation alsoforms from the strip 60 a plurality of ribs 62 that extend between andsecure together adjacent contacts. While the strip may be comprised ofany conductive, deformable material, phosphor bronze, cartridge bronzeand brass are preferred since they are inexpensive as well as conductiveand deformable.

[0064] In one embodiment, each contact 808 is comprised of a base 840that is substantially disk-shaped, and head 810 that is a smooth dome,the head projecting upward and inward from the disk edges as shown inFIGS. 3a and 3 b. In another embodiment (not shown), each base issubstantially rectangular and the head of each contact is formed of atleast one micropyramidal knurl projecting upward from the base. The headmay also have a shape of a disk, corresponding to the shape ofconductive pad 4 located on circuit board 2. Such a head would bepreferred if the material on the mating circuit board is thin and noproblems with contamination are anticipated. If an aggressive contact isrequired because of anticipated problems with contamination such as oil,oxide formation or simply metal migration due to diffusion, anaggressive head configuration such as an inverted pyramid or diamondshape could be designed. In a preferred embodiment, the periphery 43 ofthe base 40 of each head 10 has a generally rectangular outline. Eachcorner 66 of the generally rectangular outline of the base 40 is roundedand includes one of the projections 42. Each projection 42 has a roundededge 68 formed continuous with the periphery 43 of the base 40 aspreviously described.

[0065] As discussed above, depending upon the geometry of flexiblesubstrate 6, 506, 806, 906, each contact in the array of contacts willinclude a head and a base, but may or may not include a post.Furthermore, if a post is included, the length of the post will dependupon whether flexible substrate includes through holes or recesses thatdo not extend through the substrate, or combinations thereof. The shapeof the head may be any configuration that is achievable by metal workingif a stamping operation is employed, the shape of the head is determinedby the stamping die. The stamping die may include a variety of headshapes, so that the head shape may vary from position to position in thearray. While contacts may be formed by etching the metal strip, thegeometry is limited to simple profiles and lacks the flexibility thatcan be achieved by stamping.

[0066] With reference to FIG. 8, a novel method for installing formedcontacts 8 in a flexible substrate 6 is set forth. The array of formedcontacts 8 having any of the desired configurations as set forth aboveare first transferred to a flexible transfer film 70, such as, Kapton®or Mylar. For illustration purposes only, the contact configuration isas set forth in FIG. 7c, it being understood by those skilled in the artthat the contacts in the array may assume any desired shape, while thecontacts in the array are connected to one another by thin ribs, alsoformed during the stamping operation. More specifically, strip 60 havingan array of contacts 8 formed therein is aligned with the transfer film70 so that each contact 8 is aligned in registration with one of aplurality of receiving apertures 72 in the transfer film 70. This isreadily accomplished by aligning apertures 67 of strip with apertures 77of transfer film. The apertures of the transfer strip are deformable andare slightly smaller than at least a portion of the contact in order tocapture the contact. Although this process can be accomplished by anymethod, it is apparent that such alignment can be readily automated.

[0067] As shown in FIG. 9a for contacts containing a post, transfer film70 containing contacts is positioned between strip 60 and a transferbase 76 so that the posts 44 of the contacts 8 are positioned inopposition with the transfer base 76 through the receiving apertures 72of the transfer film 70. An excising tool 78 having a plurality ofblades 80 and a plurality of push pins 82 is positioned on a side of theconductive strip 60 opposite the transfer film 70. In use, the excisingtool 78 is moved towards the base 76 so that the blades 80 excisecontacts 8 from ribs 62. The excised contacts 8 are then inserted intothe receiving apertures 72 by push pins 82 so that the lengthwise axes47 of the posts 44 are substantially coaxial with lengthwise axes 83 ofthe receiving apertures 72.

[0068] Before inserting the contacts 8, each receiving aperture 72 has adiameter 84 that is less than a diagonal distance 86 (shown in FIG. 7c)between opposite comers 66 of the base 40. As shown in FIG. 10, thereceiving apertures 72 elastically deform to receive and secure theheads 10 of the contacts 8 therein. Preferably, each head 10 has aheight 88 (shown in FIG. 7c) that is greater than a thickness 90 of thetransfer film 70. Hence, when the heads 10 are inserted in the receivingapertures 72, the posts 44 of the contacts 8 are preferably positionedoutside the receiving apertures 72. When the heads 10 are received inthe receiving apertures 72, the transfer film 70 and the flexiblesubstrate 6 are positioned so that the posts 44 are in registration withand receivable in the through-holes 48.

[0069] As shown in FIG. 11, the flexible substrate 6 and the transferfilm 70 are brought together so that the posts 44 are received withinthe metallization 50 of the through-holes 48. The contacts 8 are securedto the flexible substrate 6 by fusing the posts 44 and the metallization50 of the through-holes 48 together with the solder 54.

[0070] As shown in FIG. 12, the flexibility of the transfer film 70 andthe elastic deformability of the receiving apertures 72 enables thetransfer film 70 to be separated, e.g., peeled away, from the contacts 8secured to the flexible substrate 6. When the transfer film 70 isseparated, the flexible substrate 6 and contacts 8 can be utilized inthe manner described above in connection with FIGS. 1a-1 b.

[0071] In the embodiment shown in FIG. 9b in which contact 808 includesa head 810 and a base 840, but no post, transfer film 870 is positionedbetween strip 860 and transfer base 876 so that head 810 of contacts 808are positioned in opposition with receiving cavities 899 of transferbase 876 through receiving apertures 872 of transfer film 870 and headsare inserted through apertures 872. An excising tool 878 having aplurality of blades 880 is positioned on the side of conductive strip860 opposite transfer film 870. Excising tool 878 includes a non-cuttingurging projection 881 that urges strip 860 into contact with transferfilm 870 and film 870 against transfer base 876. At least heads 810 ofcontacts 808 have a diameter greater than the diameter 884 of receivingapertures 872 of transfer film 870. Receiving apertures 872 of film 870elastically deform to receive heads 810 as heads 810 are urged intoreceiving cavities 899 of transfer base 876 by urging projection 881. Asexcising tool 878 continues its motion toward transfer base 876, blades880 of tool 878 excise contacts 808 from strip 870 by severing contacts808 from ribs 862. Transfer film 870, now containing contacts 808 isremoved from transfer base 876 and strip, is separated and removed fromfilm 870. The ribs may be cut either before or after heads are urgedinto apertures 872. The design of the excising tool can permit severingthe ribs without completely penetrating the film, after insertion ofheads into apertures 872, or alternatively can sever the ribs prior todeformation of the film by heads, the final insertion being accomplishedby push pins. With heads 810 in receiving apertures 872, transfer film870 and flexible substrate 806 are positioned so that base 840 ofcontacts 808 projecting from film 870 on the side opposite heads 810 arein registration with the preapplied conductive material 850, solderpaste, on flexible substrate 806, heads 810 of contacts 808 projectingoutward or away from the interface of transfer film 870 and flexiblesubstrate 806. Contacts 808 are secured to flexible substrate 806 in anyconventional manner such as by reflow soldering. In this embodiment,when flexible substrate 806 utilizes preapplied solder paste atpreselected positions, contacts 808 are secured to flexible substrate806 by heating to liquify the solder. After the solder has cooled,transfer film 870 is readily removed, the film elastically deforming soas to be pulled away from the contact now secured to substrate by ametallic bond having a yield strength much higher than that of film 870.As shown in FIG. 6a by way of example, a first plurality 96 ofthrough-holes 48 and a second plurality 98 of through-holes 48 arepreferably disposed on opposite sides of the flexible substrate 6. Whenthe contacts 8 are fused into the first and second plurality 96, 98 ofthrough-holes 48, the side of the flexible substrate 6 adjacent thefirst plurality 96 of through-holes 48 can be utilized to connect to onerigid substrate (not shown) and the side of the flexible substrate 6adjacent the second plurality 98 of through-holes 48 can be utilized toconnect to another rigid substrate (not shown) thereby effectingelectrical connection between the rigid substrates.

[0072] In another embodiment, each post 44 has a diameter between 7 and8 mils and a length of 2 mils. The head 30 of each contact 8 has aheight of 10 mils and the cavity 46 has a depth of 3 mils. The height ofeach projection 42 is 4 mils and a distance 94 (shown in FIG. 12)between rounded edges 68 of projections 42 on diagonally opposite corner66 is 21.5 mils. The strip 60 and contacts 8 are formed from a strip of¼ hard brass. The contacts 8 are plated with 5 micro-inches of soft goldover 30 micro-inches of palladium nickel over 50 micro-inches ofsultanate nickel. The conductors 52 and the ground planes 53 of theflexible substrate 6 are formed from ½ ounce copper which is depositedas a sheet on the flexible substrate 6 and then patterned and etchedutilizing photolithographic and etching techniques known in the art.Based on the foregoing, it can be seen that the contacts 8 aresufficiently small so that manual manipulation of contacts 8 into thethrough-holes 48 of the flexible substrate 6 is not practical. To thisend, and in accordance with the present invention, forming the array ofcontacts 8 from the strip 60 enables the contacts 8 to be manipulated asan array. Similarly, the transfer film 70 enables the contacts 8 to betransferred as an array from the strip 60 to the flexible substrate 6.The transfer film 70 also helps maintain contacts 8 in communicationwith conductive metal on the flexible substrate during fusing of thecontacts to the metallization 50 of substrate 6, the metallization beingpreapplied solder on one side of the substrate, or metallization incavities on the substrate or metallized through holes so that a strongmetallic bond can be formed. Hence, the contacts 8 are manipulated as anarray from the time they are formed from the strip 60 in the stampingoperation until they are fused onto the conductive metallization on theflexible substrate 6. This manipulation of the contacts 8 as an arrayenables the flexible circuit compression connector system of the presentinvention to be manufactured efficiently and cost effectively. Moreover,the compression connector of the present invention avoids the prior artteaching of plating contacts on the flexible substrate, and permits theuse of a variety of flexible substrates.

[0073] Because the metallization 50 at preselected locations on theflexible substrate and the conductive lines 52 are preformed on theflexible substrate 6, it is preferable to avoid soldering the contacts 8to the metallization prior to excising the contacts from the ribs 62 dueto concerns over cutting with the blades 80 of the excising tool 78 theconductive lines 52 or the metallization 50 in the through-holes 48.Hence, the contacts 8 are first transferred to the flexible transferfilm 70 which is utilized to transfer the contacts 8 to the flexiblesubstrate 6 and which may thereafter be disposed as justified by thecondition thereof.

[0074] While not described in the above embodiments, the contacts canalternatively be formed by depositing conductive metal directly onto thetransfer film, the transfer film including cavities of preselectedconfiguration corresponding to the required head, base and optional postgeometry. In this embodiment, no ribs are formed and the operation forexcising ribs is eliminated.

[0075] The various configurations of contacts of the present inventionare believed to provide over prior art systems improved contact withcontact pads 4 on the rigid substrate 2. Generally, the compressionassembly system when used with the flexible substrate forms a flexiblecircuit compression connector system that provides improved contactbetween the contact matrix on the flexible substrate and the contactpads on the rigid substrate due to the constant spring force applied bythe compression mat to the contact matrix on the flexible substrate.Furthermore, the circuit compression connector system of the presentinvention permits repeated assembly and disassembly of the flexiblesubstrate to the rigid substrate with no deterioration in electricalperformance at the interface, as the system relies on the constantspring force of the resilient mat to provide the contact force, and noton deformation of header or receptacle elements. A variety of headconfigurations for the flexible circuit compression connector system canbe made available for various applications confronted by the designer orengineer. Specifically, in one configuration, the rounded edge 68 ofeach projection 42 contacting one of the contact pads 4 cuts throughoils or films that may be present on the conductive pad 4 and/or thecontact 8 prior to mating, thereby enabling conductive paths to beformed between each projection 42 in contact with the conductive pad 4.However, less aggressive head designs such as disks or hemisphericalconfigurations can be utilized when there is concern about the integrityof the resulting connection because of thin metal. However, moreaggressive configurations can be utilized if there are concerns withcontamination or diffusion problems. In the preferred configuration, theflexible circuit compression connector system comprises a connectorblock assembly and at least one flexible substrate. This connector blockassembly can be provided as original equipment with a plurality offlexible cables for multiple connectivity, or can be readily modified atany time, such as in the field to accommodate additional flexible cablesto provide for added connectivity as the need arises.

[0076] As can be seen from the foregoing, the present invention providesa flexible circuit compression connector system that promotes electricalcontact with a conductive pad of a printed circuit board. The flexiblecircuit compression connector system of the present invention canincorporate a number of contact configurations suitable for varyingconditions that may be experienced. The invention also permits theincorporation of multiple flexible cables at any time without the needto replace existing connector system. The present invention alsoprovides a method for making a flexible circuit compression connectorsystem for use as a circuit connector that utilizes the providedcompression assembly to provide improved contact with a mating circuitconnection and is less costly to manufacture than the prior art flexiblecircuit connectors.

[0077] The invention has been described with reference to the preferredembodiment. Obvious modifications and alterations will occur to othersupon reading and understanding the preceding specification. It isintended that the invention be construed as including all suchmodifications and alterations insofar as they come within the scope ofthe appended claims or the equivalents thereof.

What is claimed is:
 1. A flexible circuit compression connector systemutilized to electrically connect together conductive pads disposed on atleast one substrate, the connector system comprising: a flexibleinsulating substrate having conductive material at a plurality ofpreselected positions, at least one conductive line thereon extendingbetween at least two of the preselected positions; a plurality ofcontacts, each contact having at least a base connected to a head ofpreselected configuration, the head extending away from the base, atleast the base of each contact secured to the flexible substrate at eachof the preselected positions having conductive material so that the headof each contact extends away from the flexible substrate; a compressionassembly including a compression mat having a plurality of resilientcolumns extending away from a base, each resilient column having adistal end alignable in registration with the flexible substrate at eachof the preselected positions on a side of the flexible substrateopposite the head; means for aligning the compression mat with theflexible insulating substrate so that the resilient columns having adistal end are in registration with the flexible substrate at each ofthe preselected positions; and means for aligning the flexible substrateand the compression assembly with at least one substrate havingconductive pads.
 2. The flexible circuit compression connector system ofclaim 1 wherein the plurality of contacts is comprised of a metallicarray of contacts at preselected positions corresponding to theconductive pads of at least one substrate in which the preselectedconfiguration is formed by stamping a thin strip of conductive metal. 3.The flexible circuit compression connector system of claim 2 wherein thepreselected configuration of at least one head is in the shape of a domeprojecting away from the base.
 4. The flexible circuit compressionconnector system of claim 2 wherein the head has a flat profile on aside of the head opposite the base.
 5. The flexible circuit compressionconnector system of claim 4 wherein the preselected configuration of atleast one head is in the shape of a disk.
 6. The flexible circuitcompression connector system of claim 4 wherein the preselectedconfiguration of at least one head is in the shape of an invertedtruncated pyramid.
 7. The flexible circuit compression connector systemof claim 4 wherein the preselected configuration of at least one head isin the shape of an inverted truncated cone.
 8. The flexible circuitcompression connector system of claim 2 wherein the preselectedconfiguration of at least one head includes at least one knurl-shapedinverted micro-pyramidal shaped projection, the tip of the pyramidprojecting away from the base.
 9. The flexible circuit compressionconnector system of claim 2 wherein the preselected configuration of atleast one head includes at least one diamond shaped projection, the tipof the diamond projecting away from the base.
 10. The flexible circuitcompression connector system of claim 1 wherein the plurality ofcontacts is comprised of a metallic array of contacts at preselectedpositions in which the preselected configuration is formed by etching athin strip of conductive metal.
 11. The flexible circuit compressionconnector system of claim 2 wherein the array of contacts formed bystamping further includes a means for aligning the array with a matingpart.
 12. The flexible circuit compression connector system of claim 11wherein the means for aligning includes at least two aperturescorresponding to apertures in the mating part.
 13. The flexible circuitcompression connector system of claim 11 wherein the means for aligningincludes at least two projections corresponding to apertures in themating part.
 14. The flexible circuit compression connector system ofclaim 2 wherein the array of contacts formed by stamping furtherincludes excisable thin ribs connecting adjacent contacts in the array.15. The flexible circuit compression connector system of claim 1 whereinthe contacts are secured to the flexible substrate at each of thepreselected positions with metallic material preapplied to thesubstrate.
 16. The flexible circuit compression connector system ofclaim 15 wherein the preapplied metallic material is solder.
 17. Theflexible circuit compression connector system of claim 1 wherein thecontacts are secured to the substrate by soldering.
 18. The flexiblecircuit compression connector system of claim 1 wherein the contacts aresecured to the substrate by reflow soldering.
 19. The flexible circuitcompression connector system of claim 1 wherein the compression assemblyfurther includes as a means for aligning the compression mat, acompression block having a top surface, a bottom surface and sidesurfaces, at least the top surface including a recess to receive andposition the compression mat on the top surface so that the resilientcolumns extend above the top surface.
 20. The flexible circuitcompression connector system of claim 19 wherein at least one additionalsurface of the compression block includes a recess to receive andposition an additional compression mat so that resilient columns of thecompression mat extend above the additional surface.
 21. The flexibleconnector system of claim 19 wherein the compression mat is attached tothe compressor block assembly with an adhesive material.
 22. Theflexible connector system of claim 21 wherein the adhesive material ispreapplied to the base of the compression mat.
 23. The flexibleconnector system of claim 20 wherein the compression block of thecompression assembly further includes at least one projection on eachsurface including the recess, the projection corresponding to at leastone aperture on the flexible insulating substrate so that the at leastone aperture receives the at least one projection and aligns theplurality of resilient columns of the compression mat with the pluralityof contacts secured to the flexible substrate.
 24. The flexible circuitcompression connector system of claim 20 wherein the means for aligningthe flexible substrate and the compression assembly with at least oneconductive pad-containing substrate includes the at least one projectionon the surface including the recess, the at least one projectioncorresponding to at least one aperture on the conductive pad-containingsubstrate so that the at least one aperture receives the at least oneprojection and aligns the plurality of contacts secured to the flexiblesubstrate to the conductive pads on the substrate.
 25. The flexiblecircuit compression connector system of claim 1 further including meansfor urging the flexible circuit compression connector system against theconductive pad-containing substrate.
 26. The flexible circuitcompression connector system of claim 20 further including means forurging the flexible circuit compression connector system against theconductive pad-containing substrate.
 27. The flexible circuitcompression connector system of claim 25 wherein the means for urgingthe flexible circuit compression connector system against the conductivepad-containing substrate includes a compression block with at least oneaperture having a counterbore, the counterbore including a threadedinsert, the aperture of the compression block corresponding to at leastone aperture of the conductive pad-containing substrate, and a memberhaving a bearing surface and a threaded end, the member extendingthrough each of the apertures, the threaded end of the member capturedby the threaded insert so that the bearing surface of the threadedmember urges together the flexible circuit compression connector systemand the conductive pad-containing substrate, the flexible circuitcompression connector system having contacts in registration with theconductive pads of the substrate.
 28. The flexible circuit compressionconnector system of claim 1 wherein the compression assembly and themeans of aligning the flexible substrate with the conductivepad-containing substrate further includes a plurality of correspondingalignment apertures in each of the flexible substrate, the conductivepad-containing substrate and the compression assembly, a plurality ofalignment pins, each alignment pin receivable through one of theplurality of alignment apertures in each of the flexible substrate, theconductive pad-containing substrate and the compression assembly,wherein the alignment apertures and the alignment pins co-act to alignthe flexible substrate, the conductive pad-containing substrate and thecompression assembly so that the heads of the plurality of contactssecured to the flexible assembly are aligned in registration with theplurality of contact pads of the substrate and the resilient columns ofthe compression mat are aligned with the flexible insulating substrateon the side of the substrate opposite the contacts.
 29. The compressionconnector as set forth in claim 28, wherein: the alignment pins arebolts, each bolt having a threaded end with external threads adapted tomate with internal threads of a threaded nut; and applying the nuts tothe bolts urges the resilient columns of the compression assemblyagainst the flexible substrate at preselected positions opposite theheads of the contacts, which in turn urges the heads against theconductive pads of the substrate to provide an electrical connection.30. The flexible circuit compression connector system of claim 1 inwhich the plurality of contacts further includes posts extending awayfrom the bases on a side of the bases opposite the heads, and theflexible substrate further includes cavities at a plurality ofpreselected positions, the cavities adapted to receive the posts of thecontacts and conductive material.
 31. The flexible circuit compressionconnector system of claim 30 in which the cavities are through-holesextending through the flexible substrate.
 32. The flexible circuitcompression connector system of claim 1 wherein the flexible insulatingsubstrate includes preselected positions having metallized through holesextending through the substrate alternating with positions havingconductive material on one side of the substrate, first conductive linesextending between at least two of the positions having conductivematerial on one side of the substrate and second conductive linesextending between at least two of the metallized through holes on a sideof the substrate opposite the positions having conductive material; anda plurality of contacts secured to the flexible substrate at each of thepreselected positions, the contacts secured to preselected positionshaving metallized through holes further including posts extending awayfrom the bases on a side of the bases opposite the heads, the postsadapted to be received by the metallized through holes, and contactssecured to alternating positions having conductive material on one sideof the substrate having at least bases connected to the heads, the headsof the plurality of contacts extending away from the flexible substrateon the side that includes the first conductive lines.
 33. The flexiblecircuit compression connector system of claim 2 wherein the preselectedconfiguration of each head is crown-shaped, having a base and aplurality of projections disposed around the periphery of the base andextending to one side thereof, and in which the contact further includesa post extending from the side of the base opposite the projections. 34.The flexible circuit compression connector system of claim 33, furtherincluding on the side of the base opposite the post a cavity inregistration with a lengthwise axis of the post.
 35. The flexiblecircuit compression connector system of claim 33 wherein each base has aperiphery having a generally rectangular outline having corners; andeach corner of the generally rectangular outline of the base is rounded.36. The flexible circuit compression connector system as set forth inclaim 35, wherein each corner of the outline of the base includes one ofthe plurality of projections, and each projection has a rounded edgeformed continuous with the periphery of each base.
 37. The flexiblecircuit compression connector system of claim 1 wherein the plurality ofcontacts includes contacts having heads of different preselectedconfigurations at preselected positions.
 38. A method for forming aflexible circuit compression connector system including a plurality ofcontacts at preselected positions, the contacts including at least abase and a head of preselected configuration, comprising the steps of:providing a flexible insulating substrate; applying conductive materialto the substrate at a plurality of preselected positions; extending atleast one conductive line between at least two of the preselectedpositions; providing a transfer film of deformable material containingan array of apertures, each aperture including a contact having at leasta base and a head of preselected configuration, the apertures beingsmaller than the contacts, the array positioned so that at least theportion of each contact opposite the head is alignable with thepreselected positions of conductive material on the flexible insulatingsubstrate; placing the transfer film against the flexible substrate sothat portions of the contacts opposite the heads abut the preselectedpositions of conductive material on the flexible substrate, while theheads project away from the flexible substrate; fusing the conductivematerial to the portion of the contacts opposite the heads; andfollowing the fusing, separating the transfer film from the flexiblesubstrate and the contacts, so that the heads of the contacts projectaway from the substrate.
 39. The method of claim 38 wherein the step ofproviding a transfer film of deformable material having apertures andcontacts further includes the additional steps of: providing a strip ofmetallic material of sufficient thickness for metal forming; forming thestrip of metallic material into an array of contacts and thin connectingribs, each contact having at least a base and a head of preselectedconfiguration connected to the base, each contact attached to theadjacent contact by the thin ribs, the contacts in the array positionedso that at least the base of each contact is alignable with thepreselected positions of conductive material on the flexible insulatingsubstrate; providing a transfer film of deformable material containingan array of apertures, the apertures being smaller than the contacts,the array of apertures positioned so that each aperture is alignablewith each contact on the formed metallic strip; aligning the contacts ofthe strip with the apertures of the transfer film; urging the transferfilm and the strip together so that the contacts are forced into theapertures, thereby deforming the apertures so that the film captures thecontacts while severing the thin ribs between the contacts; and removingthe ribs from the film containing the contacts.
 40. The method of claim39 in which the strip is formed into an array of contacts of preselectedconfiguration and thin ribs by stamping.
 41. The method of claim 40wherein the preselected configuration of the head of at least onecontact formed by stamping is in the shape of a dome projecting awayfrom the base.
 42. The method of claim 40 wherein the preselectedconfiguration of the head of at least one contact formed by stamping isa flat profile on a side of the head opposite the base.
 43. The methodof claim 40 wherein the preselected configuration of the head of atleast one contact formed by stamping is in the shape of a disk.
 44. Themethod of claim 40 wherein the preselected configuration of the head ofat least one contact formed by stamping is in the shape of an invertedtruncated pyramid.
 45. The method of claim 40 wherein the preselectedconfiguration of the head of at least one contact formed by stamping isin the shape of an inverted truncated cone.
 46. The method of claim 40wherein the preselected configuration of the head of at least onecontact formed by stamping includes at least one knurl-shaped invertedmicro-pyramidal shaped projection, the tip of the pyramid projectingaway from the base.
 47. The method of claim 40 wherein the preselectedconfiguration of the head of at least one contact formed by stampingincludes at least one diamond shaped projection, the tip of the diamondprojecting away from the base.
 48. The method of claim 38 in which thecontacts are fused to the conductive material by application of heat.49. The method of claim 38 in which the contacts are fused to conductivematerial by soldering.
 50. A transfer film of deformable materialcontaining an array of apertures, each aperture including a contactcomprised of conductive metallic material having at least a base and ahead of preselected configuration, the apertures being smaller than aportion of the contacts so that the contacts are captured by theapertures and the conductive metallic material having a higher modulusof elasticity than the transfer film, so that the transfer film can beseparated from the metallic material without deforming the metallicmaterial.
 51. The transfer film of claim 50 wherein the contacts arecomprised of: a thin sheet of metallic material stamped into an array inwhich adjacent contacts are connected by thin ribs, the contacts beingforced into the apertures to deform the apertures so that the filmcaptures the contacts.